US20140192358A1 - Color measurement apparatus - Google Patents

Color measurement apparatus Download PDF

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Publication number
US20140192358A1
US20140192358A1 US14/239,623 US201114239623A US2014192358A1 US 20140192358 A1 US20140192358 A1 US 20140192358A1 US 201114239623 A US201114239623 A US 201114239623A US 2014192358 A1 US2014192358 A1 US 2014192358A1
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United States
Prior art keywords
measurement apparatus
guiding rail
color measurement
color
casing
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Abandoned
Application number
US14/239,623
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English (en)
Inventor
Markus Barbieri
Stefan Barbieri
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Barbieri Electronic oHG Des Barbieri Siegfried & C
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Barbieri Electronic oHG Des Barbieri Siegfried & C
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Assigned to BARBIERI ELECTRONIC OHG DES BARBIERI SIEGFRIED & C. reassignment BARBIERI ELECTRONIC OHG DES BARBIERI SIEGFRIED & C. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: BARBIERI, Markus, BARBIERI, Stefan
Publication of US20140192358A1 publication Critical patent/US20140192358A1/en
Abandoned legal-status Critical Current

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/0256—Compact construction
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/0272—Handheld
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/0291—Housings; Spectrometer accessories; Spatial arrangement of elements, e.g. folded path arrangements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/10—Arrangements of light sources specially adapted for spectrometry or colorimetry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
    • G01J3/50—Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors

Definitions

  • the set of data which is representative of the producible color gamut of the printer, is compared with the known expected data for the corresponding reference colors and then it is used to calibrate the printer to correctly reproduce colors.
  • the second body is a movable measuring head and the first body is a supporting body, or base, which is stationary during a measuring movement of the second body.
  • FIG. 1 shows a perspective view of a test chart including a plurality of color patches
  • FIG. 3 shows a perspective view of a color measurement apparatus according to the present disclosure
  • FIG. 8 shows a partially cutaway top view of the color measurement apparatus according to FIG. 3 , where different operative positions are shown;
  • FIG. 9 shows a top perspective view of a measuring head of the color measurement apparatus according to FIG. 3 ;
  • FIG. 10 shows a bottom perspective view of the measuring head according to FIG. 9 ;
  • FIG. 11 shows a sectional view, according to section plane XI, of the measuring head according to FIG. 9 ;
  • FIG. 12 shows a schematic view of an operation principle of the measuring head according to FIG. 9 ;
  • FIG. 13 shows a sectional view, according to section plane XIII of FIG. 11 , of the measuring head according to FIG. 9 , from which some parts have been removed;
  • FIG. 15 shows a sectional view, according to section plane XV of FIG. 14 , of the measuring head according to FIG. 9 in the second condition, from which some parts have been removed;
  • FIG. 21 shows an exemplificative perspective view of the measuring head according to FIG. 9 on a test chart
  • FIG. 25 shows a sectional view of a second embodiment of the measuring head according to FIG. 9 ;
  • FIGS. 3 to 22 A first embodiment of a color measurement apparatus according to the present disclosure is shown in FIGS. 3 to 22 , where it is indicated by reference number 100 .
  • the color measurement apparatus 100 is intended for measuring a color on a printed item to establish a print quality of the printed item; to be more specific, the printed item is a test chart 9 .
  • FIG. 2 shows a print pattern 93 for each primary color printing.
  • each primary color is printed by a respective printing element of a printhead according to a prescribed path which, when seen in an enlarged view, appears as a print pattern.
  • the color of the patch 91 is formed by the combination and overlapping of the primary color print patterns 93 .
  • the color measurement apparatus 100 is a portable apparatus. In other words, it is easy to transport and independent from a computer, then it can be used also away from the desk and directly on a printer.
  • the measuring head 2 is movable relative to the base 1 along a direction 210 which defines a measurement path. In fact, during a measurement run, the base 1 and the test chart 9 are motionlessly resting on a support table 80 , whereas the measuring head 2 is moved along the measurement path 210 to measure a row 94 of color patches 91 .
  • the first casing 10 has a first face 11 , or bottom face, which faces the support table 80 during use, and a second face 12 , or top face opposite to the bottom face 11 , which faces a user during use.
  • the processing unit 40 is positioned inside the first casing 10 .
  • the display 42 is positioned at the top face 12 , so it can be seen by the user.
  • the display 42 is a touch-screen display.
  • the display 42 facilitates the interaction between the color measurement apparatus 100 and the user, giving also an immediate feedback about the measurement results. For example, prearranged graphic symbols or graphic elements are shown by the display 42 according to the measurement results.
  • the first casing 10 has a plurality of perimetral faces or sides between the bottom face 11 and the top face 12 .
  • the first casing 10 includes a bottom plate 17 , a top plate 18 and a plurality of side plates 19 connecting the top plate 18 to the bottom plate 17 .
  • the first face 11 is a bottom face of the bottom plate 17 and the second face 12 is a top face of the top plate 18 .
  • a first perimetral side 13 which for example is a distal side of the first casing 10 (i.e., the farther side relative to the user), is comprised between a first end 131 and a second end 132 .
  • the measuring head 2 is close to the first perimetral side 13 and, to be more specific, the movement of the measuring head 2 relative to the base 1 is a sliding movement along the first perimetral side 13 .
  • the first perimetral side 13 includes also a groove or track 138 , which is inside the cavity 137 and is parallel to the elongated direction of the latter. Moreover, the track 138 is parallel to the movement direction 210 of the measuring head 2 relative to the base 1 .
  • the window 25 is circular and it has a diameter D of 6 mm.
  • the first face 21 is a bottom face of the second casing 20 and, in use, the first face 21 faces the test chart 9 .
  • the sensor 26 is positioned inside the second casing 20 to receive light entering through the window 25 .
  • the sensor 26 is a spectral sensor or a spectrophotometer and is configured to measure color spectrum data of the received light.
  • the measuring head 2 comprises an illumination system for illuminating the test chart 9 with an illuminating light 271 .
  • a portion 273 of the illuminating light 271 is reflected by the test chart 9 , enters into the second casing 20 through the window 25 , and is received by the spectral sensor 26 .
  • the spectrum of the reflected light 273 is related to the color of the patch 91 .
  • the illumination system comprises a plurality of illuminating devices 27 .
  • Each illuminating device 27 emits a respective illuminating light beam 272 which is at an angle A of 45 degrees with the reflected light 273 , i.e. with the optical axis 260 of the spectral sensor 26 . Then the illuminating light beam 272 is at an angle of 45 degrees with the first face 21 and the test chart 9 as well.
  • the illuminating devices 27 are positioned inside the second casing 20 and around the window 25 , i.e. on a circumference 251 centered on the window 25 .
  • the illuminating devices 27 are angularly spaced from each other according to a regular distribution.
  • the illumination system comprises three illuminating devices 27 positioned on said circumference 251 at an angle B of 120 degrees from each other.
  • each illuminating device 27 comprises seven LEDs 28 different from each other.
  • the light intensity of each LED 28 can be adjusted independently from the light intensity of the other LEDs 28 .
  • the combination of the lights emitted by the LEDs 28 is an illuminating light beam 272 which almost perfectly replicates a D50 standard light source.
  • US patent application US 2011/062873 gives an example of a similar LEDs combination.
  • the guiding rail 3 comprises a first elongated member 31 , a second elongated member 32 parallel with the first elongated member 31 , and two opposite side members 33 , 34 connecting the first elongated member 31 to the second elongated member 32 .
  • the guiding rail 3 has a length L 3 .
  • the guiding rail 3 is mounted at the first perimetral side 13 of the first casing 10 .
  • the guiding rail 3 is at least partially within the cavity 137 and the first elongated member 31 is mounted on the track 138 and can slide along the track 138 .
  • the guiding rail 3 is slidingly mounted on the base 1 and can slide along the base 1 and the first perimetral side 13 in a sliding direction 310 which is parallel to the movement direction 210 of the measuring head 2 , i.e. it is parallel to the measurement path.
  • the guiding rail 3 can be in a first position or middle position which is centered between the first end 131 and the second end 132 of the first perimetral side 13 .
  • a midpoint 35 between the opposite side members 33 , 34 of the guiding rail 3 matches a midpoint 133 between the first end 131 and the second end 132 of the first perimetral side 13 .
  • the midpoint 35 is closer to the left end 131 than to the right end 132 and a left section of the guiding rail 3 is outside the cavity 137 , protruding from a left end of the cavity 137 more than in the first position.
  • the guiding rail 3 can be in a third position, where the guiding rail 3 is off-centre and protrudes from the other end of the first perimetral side 13 , for example from the right end 132 .
  • the midpoint 35 is closer to the right end 132 than to the left end 131 and a right section of the guiding rail 3 is outside the cavity 137 , being protruding from a right end of the cavity 137 more than in the first position.
  • the first, second and third positions are schematically shown in FIG. 8 , where they are at the centre, at the left and at the right in the figure, respectively.
  • the first position is between the second position and the third position. Therefore, the guiding rail 3 is reversibly movable between the first position and the second position, between the first position and the third position, and also between the second position and the third position going through the first position.
  • the second position and the third position are symmetrical.
  • the left protruding section in the second position has a length L 33 which equals the length L 34 of the right protruding section in the third position.
  • the protruding section in the second position and/or in the third position has a respective length L 33 , L 34 which is more than half of the length L 3 of the guiding rail 3 .
  • the length L 3 of the guiding rail 3 is 20 cm and the protruding sections in the second position and in the third position have respective lengths L 33 , L 34 of 15 cm.
  • the length L 3 of the guiding rail 3 is lower than, or equals, a length L 13 of the first perimetral side 13 , the length L 13 being measured between the first end 131 and the second end 132 .
  • the guiding rail 3 when the guiding rail 3 is in the first position, the guiding rail 3 is fully arranged between the first end 131 and the second end 132 of the first perimetral side 13 , i.e. it is comprised between the ends 131 , 132 of the first perimetral side 13 .
  • the guiding rail 3 is entirely within the cavity 137 and no section protrudes from any end 131 , 132 .
  • the length L 13 of the first perimetral side 13 is 20 cm.
  • Stop elements are provided to prevent the guiding rail 3 from going beyond the second position and/or the third position.
  • the stop elements are end-of-stroke stoppers which prevent the guiding rail 3 from going completely outside the cavity 137 . This is useful for avoiding any unintentional disengagement between the base 1 and the guiding rail 3 .
  • the measuring head 2 is mounted on the guiding rail 3 and can slide along the guiding rail 3 .
  • the measuring head 2 includes a slide 24 projecting from a bottom region of a side wall 23 of the second casing 20 .
  • the slide 24 is mounted on the second elongated member 32 of the guiding rail 3 and can slide along the second elongated member 32 between the two opposite side members 33 , 34 .
  • the side members 33 , 34 serve as end-of-stroke stoppers for the slide 24 and the measuring head 2 .
  • the measuring head 2 is slidingly mounted on the guiding rail 3 and can slide along the guiding rail 3 in a sliding direction which is its movement direction 210 , i.e. along the measurement path.
  • the measuring head 2 is electrically connected to the base 1 by an electric cable or wire 48 or by a bundle of cables.
  • the color measurement apparatus 100 may comprise a temperature sensor and/or a humidity sensor to measure temperature and/or humidity of the surrounding environment.
  • the measured spectral data can be influenced by the local conditions at which the measurements are carried out.
  • these temperature and/or humidity sensors are located within the base 1 .
  • the two laser pointers 52 emit beams 520 from opposite sides 22 a , 22 b , because the measuring head 2 can be moved in both ways.
  • the two beams 520 are aligned with each other and with the window 25 . Therefore, the laser pointers 52 indicate where measurements will be carried out.
  • the measuring head 2 is positioned so that the reference tongues 54 and/or the laser beams 520 are aligned with the center-line of a row 94 of consecutive color patches 91 to be measured. This is useful for assuring that the measurement direction 210 is centered relative to the row 94 of patches 91 and that an erroneous measuring of patches 91 of adjacent rows is prevented.
  • an internal side 29 a of the shutting member 29 is provided with a calibration reference target 290 , which for example is a portion with a reference white color.
  • the calibration reference target 290 is at the window 25 , i.e. it faces the spectral sensor 26 .
  • the color measurement apparatus 100 comprises also directing means for directing a translational movement of the color measurement apparatus 100 along a translation direction 110 which is perpendicular to the movement direction 210 of the measuring head 2 , i.e. it is perpendicular to the measurement path.
  • the directing means is mounted on the base 1 and includes at least one wheel or roller 51 protruding from the bottom face 11 of the first casing 10 , i.e. from the bottom plate 17 thereof.
  • the pivot 53 is inside the first casing 10 and is pivoted at seats 55 provided on a top face of the bottom plate 17 .
  • the rollers 51 a , 51 b are partially inserted into respective slots 57 made in the bottom plate 17 , so that the rollers 51 a , 51 b outwardly protrude from the bottom face 11 of the first casing 10 .
  • rollers 51 a , 51 b rotate with a same velocity about a same rotation axis 510 and any slipping of the rollers 51 a , 51 b on the support table 80 is prevented by their friction against the support table 80 itself, only a translation of the color measurement apparatus 100 along the translation direction 110 is allowed by the directing means.
  • a frictional element 59 is positioned on the bottom face 11 of the first casing 10 .
  • the frictional element 59 is close to the first perimetral side 13 , i.e. it is at the same side of the measuring head 2 and at the opposite side of the rollers 51 a , 51 b .
  • the frictional element 59 is a rubber strip which is glued to the bottom plate 17 .
  • the frictional element 59 is configured to contrast any movement of the base 1 during a measurement run, thanks to friction between the frictional element 59 and the support table 80 . This contrasting action is exerted while the frictional element 59 touches the support table 80 , then blocking the movements of the base 1 by creating a static friction force that is greater than a force acting on the base 1 during an ordinary use of the color measurement apparatus 100 .
  • the frictional element 59 blocks the movements of the base 1 along the translation direction 110 and along the movement direction 210 of the measuring head 2 .
  • the frictional element 59 is useful for keeping the base 1 motionless during a measurement run.
  • the bulge 56 prevents the frictional element 59 and the rollers 51 a , 51 b from simultaneously touching the support table 80 .
  • the base 1 can rock or swing between a first position, in which the frictional element 59 and the bulge 56 touch the support table 80 and the rollers 51 a , 51 b are raised from the support table 80 ( FIG. 19 ), and a second position, in which the rollers 51 a , 51 b and the bulge 56 touch the support table 80 and the frictional element 59 is raised from the support table 80 ( FIG. 20 ).
  • the movements of the base 1 are prevented by the frictional element 59 and then a measurement run can be carried out by moving the measuring head 2 only.
  • the color measurement apparatus 100 can move along the translation direction 110 without any contrasting action from the frictional element 59 , because the latter does not touch the support table 80 .
  • two bulges 56 are provided, each of them being button-shaped.
  • the bulges 56 are aligned with each other along a fulcrum axis 560 which is parallel to the rotation axis 510 of the rollers 51 a , 51 b and to the movement direction 210 of the measuring head 2 .
  • the bulges 56 are made of a material with a low frictional coefficient, so that the color measurement apparatus 100 in the second position can be easily moved without being hampered by friction of the bulges 56 on the support table 80 .
  • the color measurement apparatus 100 is useful for carrying out measurements on a test chart 9 which is kept stationary relative to the base 1 during a measurement run.
  • the measuring head 2 and the guiding rail 3 are initially moved to the full-left position, so that the window 25 is at the left of the first color patch 91 of the first row 94 .
  • the measuring head 2 is moved by hand 85 from the full-left position to the full-right position; the base 1 is in the first position, where it is kept motionless by the frictional element 59 touching the support table 80 .
  • a plurality of measurement regions are measured during this movement of the measuring head 2 , i.e. during a measurement run.
  • all the color patches 91 of the first row 94 are measured.
  • the spectral sensor 26 has a sampling rate of 200 Hz, therefore data are obtained for 200 measurement regions each second while the measuring head 2 is moved relative to the test chart 9 during a measurement run.
  • the window 25 is smaller than the color patch 91 (for example, the window 25 has a diameter D of 6 mm and the color patch 91 is a square having a side length of 1 cm), therefore many measurement regions can be measured for a same color patch 91 .
  • the illumination system creates an illuminating light 271 that goes out through the window 25 and illuminates the measurement region of the color patch 91 .
  • the color patch 91 reflects the illuminating light 271 ; a reflected portion 273 of the illuminating light 271 enters into the second casing 20 through the window 25 along a direction which is the optical axis 260 of the spectral sensor 26 .
  • the reflected light portion 273 whose spectrum is related to the color of the patch 91 , is received by the spectral sensor 26 , which measures the color spectrum and obtains data which are representative of the color of the respective measurement region of the patch 91 .
  • the color spectrum data are transmitted to the processing unit 40 .
  • Each measurement region can be related with a respective color patch 91 , then the color spectrum data can be compared with expected values for the same color patch 91 .
  • a distance-measuring device gives the distance of the measuring head 2 from a starting point.
  • the color patch 91 to which the measurement region is referred can be determined from the distance and the known side length of the patches 91 .
  • each measurement region can be associated with the respective color patch 91 .
  • the user presses downward the proximal region of the first casing 10 (i.e., the region of the second perimetral side 14 ) with a hand 85 to put the base 1 in the second position, wherein the rollers 51 a , 51 b touch the support table 80 and the frictional element 59 is raised.
  • the user pushes forward the color measurement apparatus 100 , until the laser pointers 52 and the reference tongues 54 are aligned with the second row 94 .
  • the forward movement is along the translation direction 110 , which is perpendicular to the rows 94 .
  • the measurement runs may be carried out always from full-left position to full-right position, or always from full-right position to full-left position.
  • the translational movement to move the color measurement apparatus 100 to a following row 94 may be carried out after having put the measuring head 2 in a central position between full-left position and full-right position.
  • spot-colors i.e. measurements carried out in specific points without effecting a whole measurement run.
  • the spectral sensor 26 may be used also to measure an ambient light, for example by directing the first face 21 and the window 25 toward a ceiling or a light source in a measurement room. This is useful for having data about the ambient light under which the test chart 9 (and also the final printed product) is watched, because the ambient light can be different from a D50 standard light.
  • the light intensity of each LED 28 can be adjusted so that the combination of the lights emitted by the LEDs 28 is an illuminating light beam 272 which replicates the measured ambient light.
  • the illumination system of the measuring head 2 is able to simulate or reproduce the ambient light, which is used during the measurements instead of a D50 standard light.
  • the adjustment of the light intensity of each LED 28 in order to reproduce such an ambient light is automatically performed by the processing unit 40 , the processing unit 40 being configured to process the measured ambient light and to accordingly set the LEDs 28 for reproducing the measured light.
  • the light 273 received by the spectral sensor 26 is a portion of a light transmitted through the test chart 9 , which for example is a film.
  • the color measurement apparatus 100 is suitable for transmissive measuring as well.
  • the illumination system is not a part of the measuring head 2 , or the illumination system is positioned outside the second casing 20 and/or the window 25 is positioned between the illumination system and the spectral sensor 26 , so that in use the test chart film is housed between the illumination system and the window 25 .
  • the processing unit 40 processes and elaborates the received data, in particular for calibration purposes of a printer and/or for determining a print quality.
  • the color measurement apparatus 100 may comprise an internal data storage to save measured color spectrum data.
  • the guiding rail 3 is a telescopic rail comprising a plurality of elongated members 30 which can slide the one relative to the other along directions 310 parallel with the movement direction 210 of the measuring head 2 .
  • the guiding rail 3 includes a series of elongated members 30 , 30 a , 30 b which can mutually slide; a first member 30 a of the series is slidingly mounted on the base 1 and the measuring head 2 is slidingly mounted on a last member 30 b of the series.
  • the digital camera 66 is positioned within the second casing 20 of the measuring head 2 , so that the digital camera 66 is movable together with the spectral sensor 26 without changing their mutual spatial relation. This means that data measured by the spectral sensor 26 can be related with an image which is simultaneously taken by the digital camera 66 .
  • the digital camera 66 is configured to receive an image of the test chart 9 through the window 25 , i.e. the image is associated with the reflected light 273 which is received through the window 25 .
  • the measuring head 2 comprises also an optical device which is able to split up the reflected light 273 between the spectral sensor 26 and the digital camera 66 .
  • the first optical axis 260 crosses the window 25 and is aligned with the direction of the reflected light 273 , i.e. the spectral sensor 26 is oriented perpendicular to the window 25 , whereas the digital camera 66 is positioned at a side between the window 25 and the spectral sensor 26 , i.e. at a side of the reflected light direction.
  • the second optical axis 660 is perpendicular to the first optical axis 260 .
  • the semi-transparent mirror 68 is positioned between the window 25 and the spectral sensor 26 , and faces the digital camera 66 .
  • the semi-transparent mirror 68 is at an angle M of 45 degrees with the direction of the incident light 273 , so that the transmitted light part 273 a is perpendicular to the reflected light part 273 b.
  • the splitting optical device is a beamsplitter prism 69 .
  • the beamsplitter prism 69 is divided into two parts 69 a , 69 b , each of them having a slanted planar surface 690 fitting perfectly to the slanted planar surface 690 of the other part.
  • At least one of the slanted planar surfaces 690 is semi-reflective, i.e. it reflects a part 273 b of the incident light 273 and transmits the remaining part 273 a of the incident light 273 . Therefore, only a part 273 a of the incident light 273 is transmitted through the beamsplitter prism 69 , whereas the remaining part 273 b of the incident light 273 is reflected by the slanted surfaces 690 .
  • the beamsplitter prism 69 is positioned between the window 25 and the spectral sensor 26 , and faces the digital camera 66 .
  • the slanted surfaces 690 of the beamsplitter prism 69 are at an angle P of 45 degrees with the direction of the incident light 273 , so that the transmitted light part 273 a is perpendicular to the reflected light part 273 b.
  • the beamsplitter prism 69 is useful for keeping the transmitted light 273 a aligned with the incident light 273 .
  • the beamsplitter prism 69 is useful for avoiding a slight misalignment between transmitted light 273 a and incident light 273 which, for a semi-transparent mirror 68 , is caused by refraction through the thickness of the mirror 68 .
  • the positions of the spectral sensor 26 and the digital camera 66 may be reverse, i.e. the spectral sensor 26 may receive the reflected light part 273 b and the digital camera 66 may receive the transmitted light part 273 a.
  • the digital camera 66 may be inside a third casing mounted on the second casing 20 or connected to the latter by a connection member, so as to be movable together as a single body.
  • the second casing 20 and the third casing are in optical communication with each other, so the second light portion 273 b reaches the digital camera 66 .
  • the positions of the spectral sensor 26 and the digital camera 66 may be reverse.
  • the digital camera 66 can be a black-and-white camera or a color camera.
  • the resolution of the digital camera 66 is sufficient for recognizing the print patterns 93 on the printed item 9, i.e. the patterns followed by each printing element of the printer which printed the test chart 9 .
  • the digital camera 66 has, for example, a resolution of 300 dots-per-inch (DPI) or greater. This resolution value is referred to the measurement region of the test chart 9 which is recorded in use; in other words, the pixel number of the digital camera 66 (for example, 2 Megapixel) required to obtain such a resolution depends also on the length of the optical path and on the features of any lens or similar optical device between the window 25 and the digital camera 66 .
  • DPI dots-per-inch
  • the digital camera 66 is a color camera, the resolution is sufficient for discriminating between primary color print patterns 93 , i.e. for recognizing each pattern 93 of the different color printing elements of the printer.
  • the reflected light portion 273 is split between the optical axis 260 of the spectral sensor 26 and the optical axis 660 of the digital camera 66 .
  • the spectral sensor 26 measures the color spectrum and obtains data which are representative of the color of the measurement region of the patch 91 .
  • the digital camera 66 takes an image of the measurement region of the patch 91 .
  • the images are processed by the processing unit 40 or by an external computer.
  • each image allows to examine small portions of the color patch 91 .
  • Each of these small portions is much smaller than the size of the window 25 and of the measurement region; for example each small portion has a size of few hundredths of millimeter, depending on the resolution of the digital camera 66 .
  • the digital camera 66 allows to measure an “image quality” of a printed item and to provide measured values of parameters that are prescribed by image quality regulations in the technical field; for example, the parameters include color uniformity, drop width, drop overlap, etc.
  • the processing unit 40 or the external computer is configured to recognize the primary color print patterns 93 in the image and to check if each print pattern 93 matches the expected pattern for the same color and/or if the color print patterns 93 are properly overlapping each other.
  • a print quality can be established from the deviations between actual spectral data/images and the reference expected value/images.
  • the printer settings are iteratively changed and adjusted until a desired print quality is met.
  • the camera 66 can also be useful for reading a code at the beginning of a row 94 ; for example the code is a line indicator or a code giving information about the color patches 91 in the respective row 94 .
  • the digital camera 66 is positioned to face the second window 67 ; its optical axis 660 crosses the second window 67 and is aligned with the direction of the respective reflected light.
  • the optical axis 660 of the digital camera 66 is perpendicular to the first face 21 , i.e. the digital camera 66 is oriented perpendicular to the second window 67 .

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  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • General Physics & Mathematics (AREA)
  • Spectrometry And Color Measurement (AREA)
US14/239,623 2011-08-31 2011-08-31 Color measurement apparatus Abandoned US20140192358A1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2011/064947 WO2013029665A1 (fr) 2011-08-31 2011-08-31 Appareil de mesure de la couleur

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US20140192358A1 true US20140192358A1 (en) 2014-07-10

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US20220326077A1 (en) * 2021-04-13 2022-10-13 Seiko Epson Corporation Color measuring apparatus
WO2024088687A1 (fr) * 2022-10-24 2024-05-02 Byk-Gardner Gmbh Appareil et procédé de mesure de propriétés optiques, en particulier d'un dispositif de mesure de couleur

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US20210293617A1 (en) * 2020-03-17 2021-09-23 InnoSpectra Corporation Spectrometer
US20220214216A1 (en) * 2020-06-28 2022-07-07 China Jiliang University Dual-optical-path spectrophotometer and color measurement method thereof
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US20220172012A1 (en) * 2020-11-30 2022-06-02 Kyocera Document Solutions, Inc. Color measurement system for printing devices
US11423267B2 (en) * 2020-11-30 2022-08-23 Kyocera Document Solutions, Inc. Color measurement system for printing devices
US20220326077A1 (en) * 2021-04-13 2022-10-13 Seiko Epson Corporation Color measuring apparatus
WO2024088687A1 (fr) * 2022-10-24 2024-05-02 Byk-Gardner Gmbh Appareil et procédé de mesure de propriétés optiques, en particulier d'un dispositif de mesure de couleur

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